DE202007008880U1 - Heat pipe - Google Patents

Abstract

Heat pipe (1) for transmission of heat between one through the heat transfer tube (1) flowing Medium and a heat transfer tube (1) surrounding medium, in particular for the withdrawal of geothermal energy, the Heating of biogas plants and for laid in building parts heating and Cooling lines, characterized in that the ratio of the pipe outside diameter (D) to the pipe wall thickness (s) greater than 11, preferably greater than 13 is.

Description

The The invention relates to a heat transfer tube for transmission of heat between one through the heat transfer tube flowing medium and a heat transfer tube surrounding medium, in particular for the withdrawal of geothermal energy, the Heating of biogas plants and for laid in building parts heating and Cooling lines.

One Heat pipe for the Withdrawal of geothermal energy, that is known from the prior art comprises an inner layer made of polyethylene PE 80 or PE 100 with a ratio of the tube outside diameter to the pipe wall thickness from 11 to 1. The pipe wall must be strong enough to one sufficient resistance against crack growth exhibit.

One such ratio From pipe diameter to pipe wall thickness leads in conjunction with the low thermal conductivity of polyethylene in the amount of 0.4 W / mK to a specific heat transfer performance of only 12 W / K per meter of pipe.

One Another known heat transfer tube for the Heating of biogas plants includes an inner layer of cross-linked Polyethylene, wherein the heat transfer tube also a relationship of the pipe outside diameter to the pipe wall thickness from 11 to 1.

These Pipes are usually used in the domestic installation, where they have 6 to 10 bar continuous operating pressure at temperatures up to 95 ° C endure and therefore must be made so thick-walled.

The low heat transfer performance is even wanted there; to further reduce these tubes are usually additionally insulated.

At the Use as a heat transfer tube in biogas plants, near the surface laid geothermal collectors and in in walls or screeds laid heat transfer tubes However, only low pressure requirements are to be met, the Heat transfer should, however, as possible be high.

Of the Invention is based on the object, the conventional heat transfer tube to the effect continue to develop, on the one hand, the specific heat transfer performance, about that but also in a particular embodiment - at least opposite pipes made of PE 80 or PE 100 - the resistance of the heat transfer tube elevated becomes.

to solution This object is achieved by the invention, the heat transfer tube according to claim 1 ready to transfer of heat between one through the heat transfer tube flowing medium and the environment is used, the ratio between outer diameter of the heat transfer tube and its wall thickness greater than 11, preferably at least 13.

In a particular embodiment has the heat pipe at least one inner layer of polypropylene (PP), polybutene (PB) or increased temperature-resistant Polyethylene (PE-RT) on.

In a further improved embodiment has the heat pipe at least one inner layer of a cross-linked polyethylene.

networked Polyethylene allows due to the excellent mechanical properties the reduction the wall thickness without loss Robustness compared to conventional non-crosslinked tubes Polyethylene.

Especially has cross-linked polyethylene virtually no so-called slow Crack growth on. By the ratio of the pipe outside diameter according to the invention to the pipe wall thickness arises opposite the conventional one Heat pipe a significantly improved heat transfer performance.

A preferred embodiment The invention relates to a heat transfer tube according to the previous embodiment, the heat transfer tube a diffusion barrier layer, preferably of ethylvinyl alcohol (EVOH) or polyamide (PA).

The Diffusion layer of EVOH or PA forms a diffusion barrier across from Oxygen, ammonia and hydrocarbons.

A further preferred embodiment The invention relates to a heat transfer tube according to one of the preceding embodiments, wherein the diffusion barrier layer has a layer thickness of 0.1 mm to 1.0 mm, preferably 0.2 mm. The diffusion barrier effect increased with increasing layer thickness. At the same time it decreases but the specific heat transfer performance of the heat transfer tube with increasing layer thickness of the diffusion barrier layer. In the area from 0.1 to 1.0 mm layer thickness of the diffusion barrier layer with regard to the barrier effect on the one hand and on the heat transfer performance On the other hand, the best results were obtained. A layer thickness of 0,2 mm proves to be ideal.

A further preferred embodiment The invention relates to a heat transfer tube according to one of the preceding embodiments, wherein between the Inner layer and the diffusion barrier layer an adhesive layer is arranged. The primer layer improves adhesion and the contact between the inner layer and the diffusion barrier layer, what the specific heat transfer performance of the heat transfer tube further improved. Preferably, the adhesion promoter layer also a higher one thermal conductivity on, as the inner layer and / or the diffusion barrier layer, what optionally be accomplished by adding additives can. Because through the adhesive layer of the contact of the adjacent layers improves the measure of providing the Adhesive layer the heat transfer performance of the heat transfer tube further.

A further preferred embodiment The invention relates to a heat transfer tube according to one of the preceding embodiments, wherein the heat transfer tube a protective layer, preferably of high density polyethylene (HDPE). This protective layer preferably forms an outer protective jacket against mechanical Effects on the heat transfer tube. The high-density polyethylene (HDPE) has a normal compared to a polyethylene Density increased thermal conductivity on what a specific heat transfer performance of the heat transfer tube continue to be beneficial is.

The The teaching of the invention also encompasses other polymeric protective layers, in particular those of crosslinked polyethylene or crosslinked polyethylene copolymers.

A further preferred embodiment The invention relates to a heat transfer tube according to one of the preceding embodiments, wherein the heat transfer tube having a primer layer under the protective layer. The Adhesive layer increased the adhesion and improves the contact between the adjacent ones Layers, resulting in a better heat transfer via the contact point of the adjacent Layers and, as a result, to a higher specific heat transfer performance of the heat transfer tube leads. Preferably For example, the primer layer has a higher thermal conductivity than the adhesive layer adjacent layers, i. as the inner layer and / or the diffusion barrier layer and / or the outer protective layer.

A another embodiment has a heat transfer tube made of cross-linked or uncrosslinked polyethylene, one on the outer circumference subsequent metallic layer and an outer polymer Protective layer on.

In a preferred embodiment is between the inner and / or the outer polymeric layer and the metallic layer disposed an adhesion promoter.

Preferred embodiments of the invention relate to heat transfer tubes according to one of the preceding embodiments, wherein the heat transfer tube has the following dimensions: outer diameter wall thickness 32mm 2,2mm 25mm 1,8mm 20mm 1.5mm 17mm 1.3mm.

These Dimensions prove to be commercial applications of the invention are particularly advantageous.

The Invention sees no limitation for the relationship the diameter of the heat transfer tube to the thickness of the outer protective layer in front. Especially with an outer protective layer made of cross-linked polyethylene, the wall thickness can also be stronger than the inner layer.

In order to can the flexibility a tube with a polymeric diffusion barrier layer or metallic layer be improved, since these usually have a higher modulus than the heat pipe, which then closer is arranged on the tube axis.

Short description the drawing

1 shows a cross-sectional view of a preferred variant of the heat transfer tube according to the invention, comprising: an inner layer, a diffusion barrier layer and an outer protective layer, wherein between the inner layer and the diffusion barrier layer and between the diffusion barrier layer and the outer protective layer adhesion promoter layers are present.

detailed Description of the invention

The invention relates to a heat transfer tube 1 for transferring heat between one through the heat transfer tube 1 flowing medium and a heat transfer tube 1 surrounding medium. The heat transfer tube 1 is particularly suitable for the withdrawal of geothermal energy and for the heating of biogas plants. The heat transfer tube according to the invention 1 includes in its simplest variant an inner layer 11 made of a cross-linked polyethylene, wherein a ratio of the pipe outside diameter (D) to the pipe wall thickness (s) greater than 13 is.

wobei:

• • λ = Wärmeleitwert,
• • r₂ = Außenradius des Rohres,
• • r₁ = Innenradius des Rohres und
• • L = Länge des Rohres.

The heat transfer capacity of a pipe is calculated according to the formula (1):

in which:

• • λ = thermal conductivity,
• • r ₂ = outer radius of the pipe,
• • r ₁ = inner radius of the pipe and
• • L = length of the pipe.

polyethylene has an average thermal conductivity of λ = 0.4 W / m · K on. High density polyethylene or high density polyethylene (HDPE) generally has a higher one thermal conductivity on, as a lower density polyethylene (LDPE).

In a preferred variant of the heat transfer tube 1 includes the heat transfer tube 1 a diffusion barrier layer 12 , preferably of barrier layer plastics such as polyvinylidene fluoride (PVDF), ethylvinyl alcohol (EVOH), ethylene tetrafluoroethylene (ETFE) or polyamide (PA). The diffusion barrier layer 12 forms a diffusion barrier to oxygen, ammonia and / or hydrocarbons. The layer thickness of the diffusion barrier layer 12 is preferably between 0.1 mm to 1.0 mm, preferably 0.2 mm. Especially with a thin-walled inner layer 11 Crosslinked polyethylene (PE-X) creates a stiffening, thicker diffusion barrier layer 12 a considerable increase in the ring stiffness of the heat transfer tube 1 , The diffusion barrier layer 12 is preferably outside the inner layer 11 arranged.

In a further preferred variant of the heat transfer tube 1 is between the inner layer 11 and the diffusion barrier layer 12 a primer layer 13 intended. The primer layer 13 preferably has a thickness of 0.1 mm and improves the adhesion and the contact between the inner layer 11 and the diffusion barrier layer 12 , The primer layer 13 preferably has a better or higher thermal conductivity than the adjacent layers, which can optionally be accomplished by adding additives. However, common adhesion promoters are also suitable for the purposes of the invention. The primer layer 13 allows an ideal contact between the inner layer from the viewpoint of heat transfer 11 and the diffusion barrier layer 13 and contributes to increase the heat transfer performance of the heat transfer tube 1 at.

In a further preferred variant of the heat transfer tube 1 has the heat pipe 1 a protective layer 14 on. The protective layer 14 protects the heat transfer tube from mechanical effects and in particular a possible diffusion barrier layer 12 against swelling on contact with water. The protective layer 14 preferably consists of high density polyethylene (HDPE) and preferably has a layer thickness of 0.1 to 1.0 mm, preferably 0.2 mm. The protective layer 14 is preferably on the outside of the heat transfer tube 1 arranged.

In a further preferred variant of the heat transfer tube 1 has the heat pipe 1 under the protective layer 14 a primer layer 15 on. The primer layer 15 improves the adhesion and the contact between the adjacent layers, ie between the inner layer 11 or the diffusion barrier layer 12 and the protective layer 14 , The primer layer 15 preferably comprises the same starting materials as the primer layer 12 , The layer thickness of the adhesion promoter layer 15 is preferably 0.1 mm.

1 shows a cross-sectional view of a preferred variant of the heat transfer tube according to the invention 1 comprising: an inner layer 11 , a diffusion barrier layer 11 outside the inner layer 11 and a protective layer 14 on the outside of the pipe, between the inner layer 11 and the diffusion barrier layer 12 and between the diffusion barrier layer 12 and the outer protective layer 14 Adhesive layers 13 . 15 available.

• 1. Wärmeübertragungsrohr 1 aus vernetztem Polyethylen (PE-X), wobei das Verhältnis Rohraußendurchmesser (D) zu Rohrwandstärke (s) größer als 11, bevorzugt größer als 13 ist;
• 2. Wärmeübertragungsrohr 1 mit einer Innenschicht 11 aus vernetztem Polyethylen (PE-X), wobei eine Diffusionssperrschicht 12 aus EVOH mit einer Schichtdicke von 0,1 mm außerhalb der Innenschicht 11 angeordnet ist, wobei ein Verhältnis Rohraußendurchmesser (D) zu Rohrwandstärke (s) größer als 11, bevorzugt größer als 13 ist;
• 3. Wärmeübertragungsrohr 1 mit einer Innenschicht 11 aus vernetztem Polyethylen (PE-X), wobei eine Diffusionssperrschicht 12 aus EVOH mit einer Schichtdicke von 0,2 bis 1,0 mm außerhalb der Innenschicht 11 angeordnet ist, wobei ein Verhältnis Rohraußendurchmesser (D) zu Rohrwandstärke (s) größer als 11, bevorzugt größer als 13 ist;
• 4. Wärmeübertragungsrohr 1 mit einer Innenschicht 11 aus vernetztem Polyethylen (PE-X), wobei eine Diffusionssperrschicht 12 aus PA mit einer Schichtdicke von 0,2 bis 1,0 mm außerhalb der Innenschicht 11 angeordnet ist, wobei ein Verhältnis Rohraußendurchmesser (D) zu Rohrwandstärke (s) größer als 11, bevorzugt größer als 13 ist;
• 5. Wärmeübertragungsrohr 1 nach 2. bis 4., wobei eine Haftvermittlerschicht 13 zwischen der Innenschicht 11 und der Diffusionssperrschicht 12 ausgebildet ist;
• 6. Wärmeübertragungsrohr 1 nach 2. bis 5., wobei eine Schutzschicht 14 aus Polyethylen an der Außenseite des Wärmeübertragungsrohrs 1 ausgebildet ist; und
• 7. Wärmeübertragungsrohr 1 nach 6., wobei eine Haftvermittlerschicht 15 unter der äußeren Schutzschicht 14 ausgebildet ist.

The preferred variants of heat transfer tubes 1 are:

• 1. heat transfer tube 1 made of cross-linked polyethylene (PE-X), wherein the ratio outside pipe diameter (D) to pipe wall thickness (s) is greater than 11, preferably greater than 13;
• 2. Heat transfer tube 1 with an inner layer 11 made of cross-linked polyethylene (PE-X), with a diffusion barrier layer 12 made of EVOH with a layer thickness of 0.1 mm outside the inner layer 11 is arranged, wherein a ratio pipe outside diameter (D) to pipe wall thickness (s) is greater than 11, preferably greater than 13;
• 3. heat transfer tube 1 with an inner layer 11 made of cross-linked polyethylene (PE-X), with a diffusion barrier layer 12 made of EVOH with a layer thickness of 0.2 to 1.0 mm outside the inner layer 11 is arranged, wherein a ratio pipe outside diameter (D) to pipe wall thickness (s) is greater than 11, preferably greater than 13;
• 4. heat transfer tube 1 with an interior layer 11 made of cross-linked polyethylene (PE-X), with a diffusion barrier layer 12 made of PA with a layer thickness of 0.2 to 1.0 mm outside the inner layer 11 is arranged, wherein a ratio pipe outside diameter (D) to pipe wall thickness (s) is greater than 11, preferably greater than 13;
• 5. heat transfer tube 1 to 2. to 4., wherein a primer layer 13 between the inner layer 11 and the diffusion barrier layer 12 is trained;
• 6. Heat transfer tube 1 after 2 to 5, with a protective layer 14 polyethylene on the outside of the heat transfer tube 1 is trained; and
• 7. heat transfer tube 1 according to 6., wherein a primer layer 15 under the outer protective layer 14 is trained.

The heat transfer tube according to the invention 1 is used in particular for the withdrawal of geothermal energy, the heating of biogas plants and for heating and cooling pipes installed in building parts. Compared to the conventional heat transfer tube, wherein the ratio of tube outside diameter to tube wall thickness at least equal 11 is and a specific heat transfer performance 12 W / m · K, has a heat transfer tube according to the invention 1 in which the ratio of pipe outside diameter (D) to pipe wall thickness (s) is the same 17 is, a specific heat transfer capacity of 20 W / m · K on. The heat transfer tube according to the invention 1 has due to the crosslinked polyethylene in the inner layer 11 excellent mechanical properties that allow no or minimal, slow crack growth.

Claims (9)

Heat transfer tube ( 1 ) for transferring heat between a through the heat transfer tube ( 1 ) flowing medium and a heat transfer tube ( 1 ) surrounding medium, in particular for the withdrawal of geothermal energy, the heating of biogas plants and laid in building sections heating and cooling lines, characterized in that the ratio of the pipe outside diameter (D) to the pipe wall thickness (s) is greater than 11, preferably greater than 13 , Heat transfer tube ( 1 ) according to claim 1, characterized in that the heat transfer tube has at least one inner layer of polypropylene (PP), polybutene (PB), elevated temperature-resistant polyethylene (PE-RT) or cross-linked polyethylene (PE-X). Heat transfer tube ( 1 ) according to claim 1, wherein the heat transfer tube ( 1 ) a polymeric and / or metallic diffusion barrier layer ( 12 ), preferably of ethylene vinyl alcohol (EVOH), polyamide (PA) or aluminum. Heat transfer tube ( 1 ) according to claim 3, wherein the diffusion barrier layer ( 12 ) has a layer thickness of 0.1 mm to 1.0 mm, preferably 0.2 mm. Heat transfer tube ( 1 ) according to claim 2 or 3, wherein between the inner layer ( 11 ) and the diffusion barrier layer ( 12 ) a primer layer ( 13 ) is arranged. Heat transfer tube ( 1 ) according to one of the preceding claims, wherein the heat transfer tube ( 1 ) an outer protective layer ( 14 ) having. Heat transfer tube ( 1 ) according to claim 6, wherein the heat transfer tube ( 1 ) and the outer protective layer ( 14 ) a primer layer ( 15 ) exhibit. Heat transfer tube according to one of the preceding claims, wherein the heat transfer tube ( 1 ) has an outer diameter (D) of about 25 mm and a wall thickness (s) of about 1.8 mm. Heat transfer tube according to one of the preceding claims, wherein the heat transfer tube ( 1 ) has an outer diameter (D) of about 20 mm and a wall thickness (s) of about 1.5 mm.